biostudies-literatureLuke CEuropean Research CouncilRoyal Societyfiag013https://www.ebi.ac.uk/biostudies/studies/S-EPMC12949516biostudies-literatureUnknown102(3)Ammonia-oxidizing archaea (AOA) are among the most abundant micro-organisms in the biosphere. They are crucial for the global nitrogen cycle through catalyzing the oxidation of ammonia to nitrite. The biochemistry, physiology, and mechanisms underlying the adaptation of AOA to diverse habitats are not fully understood, partly due to the lack of AOA pure laboratory cultures. In this study, we present the isolation of a novel species, Nitrosarchaeum marinum T12, the first Nitrosarchaeum strain isolated from a fully marine environment. We demonstrate that this AOA can grow over a vast salinity range (1-60 g l-1). Comparative genomics of Nitrosarchaeum and Nitrosopumilus strains revealed a highly diverse genetic repertoire, with many genes unique to single species. N. marinum T12 possesses genFEMS microbiology ecologyA novel North Sea ammonia-oxidizing archaeon Nitrosarchaeum marinum leverages a high abundance of transport systems to grow over a wide salinity range.PMC12949516232937DH150187852993Haaijer SCMOp den Camp HJMBespiatykh DLucker SLuke CSpeth DRJetten MSMMesman RLehtovirta-Morley LEfalseA novel North Sea ammonia-oxidizing archaeon Nitrosarchaeum marinum leverages a high abundance of transport systems to grow over a wide salinity range.Ammonia-oxidizing archaea (AOA) are among the most abundant micro-organisms in the biosphere. They are crucial for the global nitrogen cycle through catalyzing the oxidation of ammonia to nitrite. The biochemistry, physiology, and mechanisms underlying the adaptation of AOA to diverse habitats are not fully understood, partly due to the lack of AOA pure laboratory cultures. In this study, we present the isolation of a novel species, Nitrosarchaeum marinum T12, the first Nitrosarchaeum strain isolated from a fully marine environment. We demonstrate that this AOA can grow over a vast salinity range (1-60 g l-1). Comparative genomics of Nitrosarchaeum and Nitrosopumilus strains revealed a highly diverse genetic repertoire, with many genes unique to single species. N. marinum T12 possesses gen2026-01-01T00:00:00Z2026 Feb2026-07-12T03:13:02.965Z2026-07-12T03:11:07.371ZS-EPMC129495164174627710.1093/femsec/fiag013